磁耦合无线电能传输系统宽范围零电压开关实现方法

Implementation Method of Wide Range Zero Voltage Switching in Magnetic Coupling Wireless Power Transfer System

在磁耦合无线电能传输(MC-WPT)系统中,由于磁性材料和金属材料的存在,气隙变化会导致线圈自感和互感发生变化,这在小气隙应用中尤为明显。该文提出一种考虑线圈参数和负载变化的宽耦合范围零电压软开关(ZVS)实现方法。该方法使用移相调制(PSM)实现了系统的恒流/恒压(CC/CV)输出。通过优化线圈结构和补偿参数,自感变化转变为有利的可变输入阻抗,从而显著地拓宽了ZVS运行范围。同时,系统无功电流降到最小。为了验证所提方法的有效性,搭建一套250 W的实验装置,实验结果表明,在气隙变化范围10~60 mm,最大自感变化范围32.88~23.84μH,最大互感变化范围19.13~6.05μH内,系统实现了最小无功电流下的宽耦合范围ZVS运行,且具备CC/CV输出特性,峰值效率达到92.5%。

Air gap variations between coils are inevitable in magnetic coupling wireless power transfer(MC-WPT)systems.At the same time,due to the presence of magnetic and metallic materials,air gap variations can change mutual inductance and self-inductance,which is particularly evident in small air gap applications.Mutual inductance variations lead to output power fluctuation,and self-inductance variations lead to detuning and system input impedance change.Thus,achieving zero voltage switching(ZVS)in an inverter is challenging.Thus,power and efficiency are reduced.Taking the wireless charging system of an automatic guided vehicle(AGV)as an example,this paper proposes a wide coupling range ZVS implementation method for the MC-WPT system,considering coil parameters and load variations.Firstly,a time-domain analysis model of the LCC-S compensation system is established.The influence of coil parameters(mutual inductance and self-inductance)and load variations on the ZVS operation is studied.As the air gap gradually decreases,the self-inductance of the primary coil and the mutual inductance changes are not conducive to the ZVS operation,and the self-inductance changes of the secondary coil are conducive.By keeping the self-inductance in the primary coil unchanged and combining with the ZVS critical condition,the relationship between the mutual inductance and change in self-inductance of the secondary coil within the full load range is fitted,which is the ZVS operation boundary trajectory of the WPT system.Secondly,phase shift modulation(PSM)achieves constant current/voltage(CC/CV)output to charge the AGV battery.At the same time,based on the ZVS operation boundary trajectory,the self-inductance of the primary coil remains constant through coil structure and compensation parameter optimization,and the self-inductance of the secondary coil changes into a favorable variable inductive input impedance,effectively expanding the ZVS operating range of PSM.Moreover,the reactive current of the system is minimized within the full coupling range,which is beneficial for improving efficiency.Compared to the traditional ZVS range expansion method,the proposed method utilizes the parameter variation characteristics of the coil itself without additional control variables to avoid the adverse effects from self-inductance changes,which is more straightforward and more effective.Finally,a 250 W experimental platform is built to verify the correctness and effectiveness of the theoretical analysis.The experimental results show that within the air gap range of 10 mm to 60 mm,under a maximum self-inductance variation range of 32.88μH to 23.84μH and a maximum mutual inductance variation range of 19.13μH to 6.05μH,wide coupling range ZVS operation and CC/CV output are achieved with the minimum reactive current,and the peak efficiency is 92.5%.